This invention relates generally to communication networks and more particularly to a method and system for scheduling network communication
Communication devices such as telephones, computers, and video equipment may be interconnected to form a network. A network allows multiple parties to communicate with each other. Communications within a network often take the form of voice, data, video, or a combination of these forms. Such communications allow for meetings and presentations with participants separated by long distances. These events depend on the network to function as quickly and accurately as possible, in order to compensate for the distance of the participants.
A network may be formed by linking independent communication devices together according to a protocol. One example of a protocol for linking communication devices is Fibre Channel. In a Fibre Channel network, each device, acting as a node, or entry point onto the network, transmits and receives information through the network to the other network nodes. Although Fibre Channel networks may take various forms, a loop topology is often incorporated. In a loop topology, network nodes are connected in loop arrangement with any given node directly connected to only its two neighbors. In this manner, communication between all parties connected to the network is possible. One advantage of the some loop topologies is fault tolerance. In some implementations that utilize counter-rotational rings, if a break between nodes occurs, information may be routed back around the loop to its destination.
Information transmitted by the nodes travels around the loop until it reaches its destination. Traditionally, many Fibre Channel networks are configured to allow transmission of information by only one node at a given time. Thus, while any given node is transmitting information, all other nodes can only receive information. In addition traditional networking protocols do not specify the amount of time that this one node can transmit. Such communication schemes pose problems with the transmission of isochronous data that require the transfer of data at regular intervals such as live video and audio. A node that has live video to transfer is threatened with data loss if the network is currently servicing an unbounded transfer for another node. This problem is enhanced when the network has multiple sources of live isochronous data.
Such a problem may be addressed by periodically transmitting, around a network, a plurality of frames that include a plurality of slots for storing information. In such a system, it is desirable to be able to allocate priorities to the frames and to specify the time in which such frames are transmitted. Furthermore, it is also desirable to be able to specify a rate at which frames are transmitted.
Accordingly, a need has arisen for an improved method and system for network communication. The present invention provides a method and system for communication information in a network that addresses shortcomings of prior systems and methods.
According to one embodiment of the invention, a method for communicating information in a network having a plurality of nodes includes providing a frame for storing information. The frame has a frame type. The method also includes determining the type of the frame. In response to determining the frame type, scheduling transmission of the frame from a node in the network is scheduled. The method also includes transmitting the frame at the scheduled time.
According to another embodiment of the invention, an apparatus for scheduling periodic transmission of a plurality of frames in a network having a plurality of nodes, each frame having a type, includes a schedule memory and a sequencer. The schedule memory stores a transmission time for each frame type and a list of frames to be transmitted. The sequencer is operable to access the schedule memory and initiate transmission of the frames in the list.
Embodiments of the invention provide numerous technical advantages. For example, in one embodiment of the invention, a plurality of frames of data may be transmitted around a network at different periodic rates. Furthermore, these frames may be specified to carry different amounts of data. Such transmission provides an efficient method of communication because smaller frames may be used to carry smaller amounts of data and frames that are transmitted at a slower periodic rate may be used for data that does not require a faster rate of transmission. The invention also allows transmission of aperiodic frames when bandwidth is available which is also efficient.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.